I would love too see Gundams. Most particularly ones from Mobile Suit Gundam, 08th MS Team, 0079, 0080, 0083, Char's Counterattack, Gundam V, Gundam Z, and Gundam ZZ. Gundam Wing, Endless Waltz, and Gundam SEED units would be awesome as well.
Of course you could do Gundam X units because there is atleast 1 which represents a country in the battle tournament.. but they're unrealistic and that series I think was the worst one because it had a different director/writer and it was completely unrealistic and different from the original timelines... people controlling a massive mech by moving and being hooked up with signals which make the Gundam move.. bleh.. I hate that series!
Gundam X mechs although unrealistic.. are kind of cool. Spain's has bull horns, Mexico's has a sombrero, Canada's is a lumber jack, UKs looks like a beefeater... and of course Japan has the main Gundam and 5 other ones.
There is one Gundam unit on this forum, I think it's horrible.
Transformers is about vehicles like trucks, trains, and boats turning into mechs. Gundam is about countries and space colonies around the 22nd century creating mechs and fighting battles all over.. and these mechs are pretty realistic. The story is sophisticated, made for adults, and well thought out in a historical sense. Haha, a union of space colonies formed by the Duchy of Zeon, a smaller space colony, taking over using German WWII strategies, landing on Earth and conquering Australia, Malaysia, and some of South America in a few weeks and even saying "Sieg Zeon" to praise their leader Char Aznable.